Lennox E250 Error Code — What It Means
E250 on a Lennox furnace means the limit switch circuit is open. The furnace control is not seeing the high-limit safety switch closed during a heating cycle. This is a safety condition tied to overheat protection or a circuit fault in the limit chain. When the limit does not close within three minutes, the control enters a one-hour soft lockout. Normal operation resumes after the fault clears.
Common Causes
- Restricted airflow causing overheating Dirty filter, blocked registers, closed return or supply vents, or obstructed ductwork prevent proper air movement over the heat exchanger and trigger the limit.
- Failed or stuck-open limit switch The high-limit switch itself can fail in the open position or stick open, making the control think there is an overheat condition even when airflow is adequate.
- Blower motor or module failure If the blower motor or its control module is not running or moving enough air, the heat exchanger overheats and the limit opens.
- Wiring or harness fault in the limit circuit Loose connections, damaged wiring, or corroded terminals between the limit switch and the control board cause an open circuit.
- Incorrect gas input or firing rate Overfiring or an improperly set gas valve can produce excessive heat that trips the limit even with adequate airflow.
Step-by-Step Fix
- Confirm the E250 code on the control display and note whether any other faults are present at the same time.
- Check airflow restrictions by inspecting the filter, verifying all supply and return registers are open, and looking for blockages in the ductwork or at the unit itself.
- Inspect the high-limit switch and its wiring for loose or corroded connections, damaged harness, or physical signs of failure on the switch.
- Verify the blower is running during a call for heat and check that 120 VAC is present across L1 and Neutral at the integrated control during motor operation.
- Test the gas firing rate if overheating is suspected and airflow is confirmed adequate, adjusting the gas valve or input to manufacturer specifications if needed.
- Replace the failed component, whether that is the limit switch, blower motor, blower module, or damaged wiring, then clear the fault.
- Restore power and run a full heating cycle to confirm the furnace operates normally and the E250 does not return.
Parts Often Needed
| Part | Notes |
|---|---|
| High-limit switch | Amazon | Match the switch to your model and voltage rating if it tests open or fails to close. |
| Blower motor | Amazon | Required if the motor does not run or is not moving adequate air for your tonnage. |
| Blower control module | Amazon | For variable-speed systems where the module has failed or is not commanding the blower properly. |
| Integrated furnace control board | Amazon | If the control is not supplying the proper circuit path or voltage to the motor or limit circuit. |
When to Call a Pro
Call a qualified HVAC technician if you have checked the filter and airflow and the code persists, if you are not comfortable working with line voltage (120 VAC) or gas systems, or if you need to test the limit switch or blower circuit with a multimeter. A technician can verify proper firing rate, diagnose control board or blower module faults, and safely replace wiring or components in the limit safety circuit.